Why would Openreach need to read anything when they have provided a facility for ISPs to check the status of the line and that checker correctly shows that there is a waitlist (as evidenced by the BT Wholesale checker showing it). It is not Openreach's problem if their customers (the ISPs) cannot read - maybe you should be directing your ire at them?
What is Openreach's process for extending cabinet capacity at a given location? TBH, a waiting list is hardly an acceptable solution as I would imagine the number of people who (intentionally!) cancel their internet service now is pretty low, unless there is some alternative (e.g. an altnet) available to them.
Can an ISP request this from OR or is there some automatic process based on the number of premises waiting for connection? It would be a bit daft if, as I presume is the case, most ISPs won't accept orders for connections on a waiting list, thus there's little feedback to OR that they are under-capacity in a given location. "Oooh, look. We have exactly the right amount of provision at all of these cabinets because they are all exactly 100% utilised with noone waiting for a connection!"
A question to OP too - I assume you've checked that there's no other altnet operating in the area, and none planning any deployments? This is hard to know as there's not really any centralised way to check, but it might be worth a look around your area to see if there's any sign of FTTP provision nearby.